Underbelly scabbed up and snake wont eat

[Riley]

A little over a month ago my ball python swallowed a piece of bedding with a mouse and I could tell it tore him up a little bit inside but he didnt seem too effected by it. After his most recent shed, his underbelly looked pretty torn up, I was guessing it was from the woodchip he swallowed and figured he would heal. Well it has been three weeks since he has eaten (usually eats once a week) and his belly has gotten MUCH worse, the part that was torn up now looks scabbed up. He seems hungry, but when a mouse goes near him he gets scared and tries to hide. I think he is affraid the mouse may harm him while he is injured. I tried feeding him frozen and he won't go for it. I have been putting coconut oil on the effected area and trying to feed him periodically, but I am beginning to worry. I also wondered if it was from my undertank heater so I have stopped using that. Can someone tell me what to do next? Is he okay to fast until he is healed?

[Pareeeee]

It looks like a bad burn turned scale rot to me. You need to take him to a vet ASAP if you haven't already.

Do not let his enclosure get cold; that can cause other serious health problems. You need to buy a digital thermostat for your under tank heater to control the temps and prevent it from causing more burns.

What are your tank specs? Humidity, temps, substrate, etc?

[Albert Clark]

Absolutely a critical burn here! Sorry to see this. The animal needs a qualified exotic vet. This is a emergency. The exotic vet needs to know you need to be scheduled in immediately if the snakes prognosis is to be good.

[Piggybuns]

This is definitely from the undertank heater, but you can't just turn it off; snakes need heat. It has to be regulated by a thermostat, the way Pareeeee said, it can keep it from getting too hot. There's not a lot anyone on this board can do for that, that is some serious damage. Get to a vet!
:EDIT: Also there's no possible way a woodchip did that if he swallowed it unless it literally slitted him from the inside, in which... VET?

[Tiny Boidae]

Poor little fella! A vet visit is absolutely 110% mandatory at this point, otherwise that snake will probably end up dying. As others have said, get a thermostat for the UTH and don't just unplug it. What would also probably help is getting out the wood chippings you have in there now and do a really good scrub down of the cage to get it as clean and sterile as possible. Instead of replacing it with more wood chippings, I would use paper towel or something similar. While he's being treated, clean the cage weekly or anytime he soils it with the use of reptile-safe disinfectants. Also, make sure the humidity stays up but don't soak the substrate as that would only aggravate the problem.